How, you ask? Well, ponder this.Say a person went around life with a severe hatred of the color orange. And not as in "oh this orange shirt does nothing for my complexion" hate, but hate as in a sincere belief that anything bearing this color is pure evil, sinful, and must be eradicated. The belief that orange is the cause for all that is wrong with the world. Even going so far as to brutally attacking/killing people for merely wearing the color orange.You'd think that person was a prime candidate for the nuthouse, right?Now go over that scenario again, but replace 'the color orange' with 'homosexuality'.Yeah.

Just a lil nitpick, but the term you want is mental illness. Disease is something that can spread biologically, but mental illness are things like depression, anxiety ext which is what this would come under

I think not understanding someone's opinion is more of a disease than homophobia in itself. And before anyone flips their shit, I am for gay rights/marriage/etc.

Firstly, your "argument", if you would even call it that, is highly ridiculous. Secondly, there are people who will call ANYBODY a homophobe all just because they do not believe in gay marriage, regardless if it has any correlation to the actual hatred/discrimination/judgment of homosexuality. You cannot expect people who have followed the Bible their whole lives to suddenly revert to your opinion just because you it is right. (Although you do not have to be Christian to be against such - just bare with me because this is the majority here.)

I feel like there is more discrimination to people who are against it than there are people for it. And it is ironic - not in the funny way either.

It is not a mental disease. Your comparison is obsolete because homophobia is something you learn from other people. One does not get homophobic without being influenced into being so, on arguably a large amount of occasions. If you apply your 'orange' situation to heterosexuality, then there are practically zero people who hate it. An irrational hatred of the color orange is a mental disorder as there are no justifiable reasons to hate it. If an individual is homophobic but does not let this stance of homosexuals control their minds and make them want to kill people, it is not a disease, merely an opinion. One that goes far enough to attack and murder an individual could be considered to have a 'mental disease' as you put it however I am not sure about defining it that way.